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    <title>Document</title>
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    <script>
        //1.如果函数体只有一行return，可以省略return和大括号，
        let a = (m, n) => m + n
        //2.形参赋值默认值
        let c = (m = 0, n = 0) => m + n
        //3.箭头函数中没有arguments,但可以使用剩余运算符获取传递的实参集合
        let s = (...arg) => {
            return eval(arg.join('+'))
        }
        //4.简单
        function sum(m) {
            return function (n) {
                return m + n
            }
        }
        let x = (m) => (n) => m + n

    </script>
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